EVANS CITY — A Butler County woman says state environmental officials refused to do follow-up tests after their lab reported her drinking water contained chemicals that could be from nearby gas drilling.

At least 10 households in the Woodlands community have complained that recent natural gas drilling impacted their water in different ways.

The Department of Environmental Protection first suggested that Janet McIntyre’s well water contained low levels of only one chemical, toluene. But a review of the DEP tests by The Associated Press found four other volatile organic compounds in her water that can be associated with gas drilling.

DEP spokesman Kevin Sunday said on Friday that the low chemical concentrations were not a health risk, and suggested that the contamination may have come from the agency’s laboratory itself or from abandoned vehicles on or near the property. But Sunday didn’t answer why DEP failed to do follow-up tests if the DEP suspected that its own lab was contaminated.

One public health expert said the lack of follow-up tests by DEP doesn’t make sense.

“DEP cannot just simply walk away,” said Dr. Bernard Goldstein, professor emeritus at the University of Pittsburgh School of Public Health.

McIntyre and other residents say the water problems started about a year ago, after Rex Energy of State College drilled two wells. But a map Rex provided also shows gas wells from other companies in the area.

Residents in the community have been complaining for nearly a year, but DEP never revealed the possible presence of chemicals to the public.

Rex has been supplying drinking water to many households, but it has sent letters notifying them it will no longer deliver the water after Feb. 29.

In a statement, Rex said that the wells of residents who have complained are from 2,100 to 4,600 feet from its drilling locations. The company noted that many other homeowners in the area haven’t raised concerns.

Rex also said there are old oil wells in the region that could impact some ground water, and that there were “no notable differences in water chemistry between pre- and post-drill water quality tests of the water wells in question.”

McIntyre’s water showed detectable levels of t-Butyl alcohol, acetone, chloromethane, toluene and 1, 3, 5-trimethylbenzene. The chemicals can be used in the high-pressure hydraulic fracturing process that has led to a production boom of deep shale gas in Pennsylvania. But some are also commonly used in households and other industry.

Goldstein said the multi-chemical mix is what is so unusual, since it suggests either multiple sources of contamination, or an industry that uses many different chemicals.

“Where would you get such a strange mixture?” Goldstein asked. “Is this coming from drilling?”

He added that the low concentrations shown in the test may not be a health threat, and may not be connected to gas drilling. But if DEP’s own laboratory was even a potential source of the chemicals, the agency had the obligation to follow up.

“You’ve got to pursue the finding,” Goldstein said, since if the lab was at fault the variety of chemicals that showed up “makes no sense at all, except a really sloppy lab.”

Sunday said an independent peer review of the DEP laboratory found it to be “a well-managed, efficient and highly functional laboratory.”

McIntyre told the AP that she repeatedly asked a DEP field worker for follow-ups after two separate tests last summer showed the chemicals, as well as elevated levels of some natural underground compounds such as barium.

“He said no,” she said, leaving her feeling that she had no one to turn to for an objective public health opinion.